1. R. A. Abdellatif: Ph. D. Thesis, University of Washington, unpublished (1970).
2. K. Johnson: private communication.
3. S. L. Adler:Phys. Rev. D,6, 3445 (1972);7, 3821(E) (1973).
4. N. Christ:Phys. Rev. D,9, 946 (1974).
5. J. Ngak-Hua Ng: Ph. D. Thesis, University of Washington, unpublished (1974).